Electromagnetic energy distributions for electromagnetically induced mechanical cutting

ABSTRACT

Output optical energy pulses including relatively high energy magnitudes at the beginning of each pulse are disclosed. As a result of the relatively high energy magnitudes which lead each pulse, the leading edge of each pulse includes a relatively large slope. This slope is preferably greater than or equal to 5. Additionally, the full-width half-max value of the output optical energy distributions are between 0.025 and 250 microseconds and, more preferably, are about 70 microseconds. A flashlamp is used to drive the laser system, and a current is used to drive the flashlamp. A flashlamp current generating circuit includes a solid core inductor which has an inductance of 50 microhenries and a capacitor which has a capacitance of 50 microfarads.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation co-pending U.S. application Ser. No.11/606,660, filed Nov. 29, 2006 now U.S. Pat. No. 7,415,050 and entitledELECTROMAGNETIC ENERGY DISTRIBUTIONS FOR ELECTROMAGNETICALLY INDUCEDMECHANICAL CUTTING, which is a continuation-in-part of co-pending U.S.application Ser. No. 11/523,492, filed Sep. 18, 2006 now U.S. Pat. No.7,696,466 and entitled ELECTROMAGNETIC ENERGY DISTRIBUTIONS FORELECTROMAGNETICALLY INDUCED MECHANICAL CUTTING, all of which arecommonly assigned and the contents of which are expressly incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to lasers and, moreparticularly, to devices for generating output optical energydistributions.

2. Description of Related Art

A variety of laser systems are present in the prior art. A solid-statelaser system generally comprises a laser rod for emitting coherent lightand a stimulation source for stimulating the laser rod to emit thecoherent light. Flashlamps are typically used as stimulation sources forErbium laser systems, for example. Diodes may be used instead offlashlamps for the excitation source. The use of diodes for generatinglight amplification by stimulated emission is discussed in the bookSolid-State Laser Engineering, Fourth Extensively Revised and UpdatedEdition, by Walter Koechner, published in 1996, the contents of whichare expressly incorporated herein by reference.

Prior art laser diode pumped lasers have been either end-pumped, asdemonstrated in FIG. 1 a or side-pumped. End pumping configurations canbe more efficient and can produce a better transverse mode. In FIG. 1 a,wherein “HR” denotes a high reflectivity element and “OC” denotes anoutput coupling element, laser output is focused into a fiber via alens. Side pumping constructions, on the other hand, can be morescalable therefore enabling the generation of relatively high laserpower and energy.

The excitation source (e.g., flashlamp) is driven by a current (e.g., aflashlamp current), which comprises a predetermined pulse shape and apredetermined frequency. The flashlamp current drives the flashlamp atthe predetermined frequency, to thereby produce an output flashlamplight distribution having substantially the same frequency as theflashlamp current. This output flashlamp light distribution from theflashlamp drives the laser rod to produce coherent light atsubstantially the same predetermined frequency as the flashlamp current.The coherent light generated by the laser rod has an output opticalenergy distribution over time that generally corresponds to the pulseshape of the flashlamp current.

The pulse shape of the output optical energy distribution over timetypically comprises a relatively gradually rising energy that ramps upto a maximum energy, and a subsequent decreasing energy over time. Thepulse shape of a typical output optical energy distribution can providea relatively efficient operation of the laser system, which correspondsto a relatively high ratio of average output optical energy to averagepower inputted into the laser system.

The prior art pulse shape and frequency may be suitable for thermalcutting procedures, for example, where the output optical energy isdirected onto a target surface to induce cutting. New cuttingprocedures, however, do not altogether rely on laser-induced thermalcutting mechanisms. More particularly, a new cutting mechanism directsoutput optical energy from a laser system into a distribution ofatomized fluid particles located in a volume of space just above thetarget surface. The output optical energy interacts with the atomizedfluid particles causing the atomized fluid particles to expand andimpart electromagnetically-induced mechanical cutting forces onto thetarget surface. As a result of the unique interactions of the outputoptical energy with the atomized fluid particles, typical prior artoutput optical energy distribution pulse shapes and frequencies have notbeen especially suited for providing optical electromagnetically-inducedmechanical cutting. Specialized output optical energy distributions arerequired for optimal cutting when the output optical energy is directedinto a distribution of atomized fluid particles for effectuatingelectromagnetically-induced mechanical cutting of the target surface.

SUMMARY OF THE INVENTION

The output optical energy distributions of the present inventioncomprise relatively high energy magnitudes at the beginning of eachpulse. As a result of these relatively high energy magnitudes at thebeginning of each pulse, the leading edge of each pulse comprises arelatively large slope. This slope is preferably greater than or equalto 5. Additionally, the full-width half-max (FWHM) values of the outputoptical energy distributions are greater than 0.025 microseconds. Morepreferably, the full-width half-max values are between 0.025 and 250microseconds and, more preferably, are between 10 and 150 microseconds.The full-width half-max value is about 70 microseconds in theillustrated embodiment. A flashlamp is used to drive the laser system,and a current is used to drive the flashlamp. A flashlamp currentgenerating circuit comprises a solid core inductor having an inductanceof about 50 microhenries and a capacitor having a capacitance of about50 microfarads.

In accordance with one aspect of the present invention, a method ofcutting or ablating hard tissue is disclosed, comprising the steps ofproviding a gain medium, a diode array, and an optical cavity; placingthe gain medium and the diode array within the optical cavity so thatthe diode array is optically aligned to side pump the gain medium;activating the diode array to light pump the gain medium and generatelaser light; and directing the laser light onto the hard tissue to cutor ablate the hard tissue.

In accordance with another aspect of the present invention, a method ofcutting or ablating hard tissue, comprises the steps of providing a gainmedium, a diode light pump, and an optical cavity; placing the gainmedium and the diode light pump within the optical cavity so that thediode light pump is optically aligned to light pump the gain medium;activating the diode light pump to light pump the gain medium andgenerate laser light; and directing the laser light onto the hard tissueto cut or ablate the hard tissue.

According to another aspect of the invention, an apparatus for cuttingor ablating hard tissue, comprises an optical cavity; a gain mediumdisposed within the optical cavity; a diode light pump disposed withinthe optical cavity and optically aligned to light pump the gain mediumto generate laser light, wherein the generated laser light has awavelength and power density suitable for cutting and ablating hardtissue.

In any of the above aspects, the gain medium may comprise a laser rod,such as an Erbium-based laser rod. More particularly, the gain mediummay comprise an Erbium-based crystalline laser rod for generating laserlight in a range between 1.73 and 2.94 microns. The laser light can begenerated in the TEMoo mode to overcome thermal effects. In accordancewith a method of the present invention, the hard tissue can comprise,for example, tooth or bone tissue. Temporal pulse control can be used toattain a uniform temporal pulse pattern. In another embodiment, gainswitching or Q-switching can be used to attain the uniform temporalpulse pattern. The diode light pump can comprise a diode array, and thediode array can be optically aligned to side pump the gain medium. Thediode light pump can be placed within the optical cavity so that thediode array is optically aligned to side pump the gain medium.

While the apparatus and method has or will be described for the sake ofgrammatical fluidity with functional explanations, it is to be expresslyunderstood that the claims, unless expressly formulated under 35 USC112, are not to be construed as necessarily limited in any way by theconstruction of “means” or “steps” limitations, but are to be accordedthe full scope of the meaning and equivalents of the definition providedby the claims under the judicial doctrine of equivalents, and in thecase where the claims are expressly formulated under 35 USC 112 are tobe accorded full statutory equivalents under 35 USC 112.

Any feature or combination of features described herein are includedwithin the scope of the present invention provided that the featuresincluded in any such combination are not mutually inconsistent as willbe apparent from the context, this specification, and the knowledge ofone skilled in the art. In addition, any feature or combination offeatures may be specifically excluded from any embodiment of the presentinvention. For purposes of summarizing the present invention, certainaspects, advantages and novel features of the present invention aredescribed. Of course, it is to be understood that not necessarily allsuch aspects, advantages or features will be embodied in any particularimplementation of the present invention. Additional advantages andaspects of the present invention are apparent in the following detaileddescription and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of flashlamp-driving current versus time according tothe prior art;

FIG. 2 is a plot of output optical energy versus time for a laser systemaccording to the prior art;

FIG. 3 is a schematic circuit diagram illustrating a circuit forgenerating a flashlamp-driving current in accordance with the presentinvention;

FIG. 4 is a plot of flashlamp-driving current versus time in accordancewith the present invention;

FIG. 5 is a plot of output optical energy versus time for a laser systemin accordance with the present invention;

FIG. 6 is a block diagram showing a fluid output used in combinationwith an electromagnetic energy source having a flashlamp driving circuitin accordance with the present invention;

FIG. 1 a is a schematic illustration of an end-pumped diode laser inaccordance with the prior art;

FIG. 1 b is a side-pumped diode laser according to the presentinvention;

FIG. 2 a is a schematic top view of a laser head according to thepresent invention;

FIG. 2 b is a schematic side view of a laser head according to thepresent invention;

FIG. 3 a is a regulated laser pulse format according to the presentinvention;

FIG. 4 a shows the population inversion in a CW pumping regime accordingto the present invention;

FIG. 4 b shows the resonator Q due to the Q-switch hold-off according tothe present invention;

FIG. 4 c shows the resulting laser pulse from FIGS. 4 a and 4 baccording to the present invention;

FIG. 5 a shows the quasi CW current supplied to the pumping laser diodeaccording to the present invention;

FIG. 5 b shows the population inversion in the quasi CW pumpingaccording to the present invention;

FIG. 5 c shows resulting laser pulse from FIGS. 5 a and 5 b according tothe present invention;

FIG. 6 a is a representation corresponding to a preferred pulse shape;and

FIG. 7 is a close-up view of a pulse of FIG. 6 a.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to particular embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same or similar reference numbers areused in the drawings and the description to refer to the same or likeparts. It should be noted that the drawings are in simplified form andare not to precise scale. In reference to the disclosure herein, forpurposes of convenience and clarity only, directional terms, such as,top, bottom, left, right, up, down, over, above, below, beneath, rear,and front, are used with respect to the accompanying drawings. Suchdirectional terms should not be construed to limit the scope of theinvention in any manner.

Although the disclosure herein refers to certain illustratedembodiments, it is to be understood that these embodiments are presentedby way of example and not by way of limitation. The intent of thefollowing detailed description, although discussing exemplaryembodiments, is to be construed to cover all modifications,alternatives, and equivalents of the embodiments as may fall within thespirit and scope of the invention as defined by the appended claims.

Referring more particularly to the drawings, FIG. 1 illustrates a plotof flashlamp-driving current versus time according to the prior art. Theflashlamp-driving current 10 initially ramps up to a maximum value 12.The initial ramp 14 typically comprises a slope (current divided bytime) of between 1 and 4. After reaching the maximum value 12, theflashlamp-driving current 10 declines with time, as illustrated by thedeclining current portion 16. The prior art flashlamp-driving current 10may typically comprise a frequency or repetition rate of 1 to 15 hertz(Hz). Additionally, the flashlamp-driving current 10 of the prior artmay typically comprise a pulse width greater than 300 microseconds. Thefull-width half-max value of the flashlamp-driving current 10 istypically between 250 and 300 microseconds. The full-width half-maxvalue is defined as a value of time corresponding to a length of thefull-width half-max range plotted on the time axis. The full-widthhalf-max range is defined on the time axis from a beginning time, wherethe amplitude first reaches one half of the peak amplitude of the entirepulse, to an ending time, where the amplitude reaches one half of thepeak amplitude a final time within the pulse. The full-width half-maxvalue is the difference between the beginning time and the ending time.

FIG. 2 illustrates a plot of energy versus time for the output opticalenergy of a typical prior art laser. The output optical energydistribution 20 generally comprises a maximum value 22, an initial ramp24, and a declining output energy portion 26. The micropulses 28correspond to population inversions within the laser rod as coherentlight is generated by stimulated emission. The average power of thelaser can be defined as the power delivered over a predetermined periodof time, which typically comprises a number of pulses. The efficiency ofthe laser system can be defined as a ratio of the output optical powerof the laser, to the input power into the system that is required todrive the flashlamp. Typical prior art laser systems are designed withflashlamp-driving currents 10 and output optical energy distributions 20which optimize the efficiency of the system.

FIG. 3 illustrates a flashlamp-driving circuit 30 according to thepresently preferred embodiment. The flashlamp-driving circuit 30comprises a high-voltage power supply 33, a capacitor 35, a rectifier37, an inductor 39, and a flashlamp 41. The capacitor 35 is connectedbetween the high-voltage power supply 33 and ground, and the flashlamp41 is connected between the inductor 39 and ground. The high-voltagepower supply 33 preferably comprises a 1500 volt source, having acharging rate of 1500 Joules per second. The flashlamp 41 may comprise a450 to 700 torr source and, preferably, comprises a 450 torr source. Thecapacitor 35 preferably comprises a 50 microfarad capacitor, and therectifier 37 preferably comprises a silicon-controlled rectifier. Theinductor 39 preferably comprises a 50 microhenry solid-core inductor. Inalternative embodiments, the inductor 39 may comprise a 13 microhenryinductance. In still other alternative embodiments, the inductor 39 maycomprise inductance values of between 10 and 15 micro-henries. Othervalues for the inductor 39 and the capacitance 35 may be implemented inorder to obtain flashlamp-driving currents having relatively largeleading amplitudes, for example, as discussed below.

The output optical energy distribution 60 of the present invention isuseful for maximizing a cutting effect of an electromagnetic energysource 32, such as a laser driven by the flashlamp driving circuit 30,directed into an atomized distribution of fluid particles 34 above atarget surface 36, as shown in FIG. 6. An apparatus for directingelectromagnetic energy into an atomized distribution of fluid particlesabove a target surface is disclosed in U.S. Pat. No. 5,741,247, entitledATOMIZED FLUID PARTICLES FOR ELECTROMAGNETICALLY INDUCED CUTTING. Thehigh-intensity leading micropulses 64, 66, and 68 impart large amountsof energy into atomized fluid particles which preferably comprise water,to thereby expand the fluid particles and apply mechanical cuttingforces to the target surface of, for example, tooth enamel, toothdentin, tooth cementum, bone, and cartilage, skin, mucosa, gingiva,muscle, heart, liver, kidney, brain, eye or vessels. The trailingmicropulses after the maximum micropulse 68 have been found to furtherenhance the cutting efficiency. According to the present invention, asingle large leading micropulse 68 may be generated or, alternatively,two or more large leading micropulses 68 (or 64, 66, for example) may begenerated.

The incoherent light from the presently preferred flashlamp 41 impingeson the outer surface of the laser rod. As the incoherent lightpenetrates into the laser rod, impurities within the laser rod absorbthe penetrating light and subsequently emit coherent light. Theimpurities may comprise erbium and chromium, and the laser rod itselfmay comprise a crystal such as YSGG, for example. The presentlypreferred laser system comprises either an Er, Cr:YSGG solid statelaser, which generates electromagnetic energy having a wavelength in arange of 2.70 to 2.80 microns, or an erbium, yttrium, aluminum garnet(Er:YAG) solid state laser, which generates electromagnetic energyhaving a wavelength of 2.94 microns. As presently preferred, the Er,Cr:YSGG solid state laser has a wavelength of approximately 2.78 micronsand the Er:YAG solid state laser has a wavelength of approximately 2.94microns. According to one alternative embodiment, the laser rod maycomprises a YAG crystal, and the impurities may comprise erbiumimpurities. A variety of other possibilities exist, a few of which areset forth in the above-mentioned book Solid-State Laser Engineering,Fourth Extensively Revised and Updated Edition, by Walter Koechner,published in 1996, the contents of which are expressly incorporatedherein by reference. Other possible laser systems include an erbium,yttrium, scandium, gallium garnet (Er:YSGG) solid state laser, whichgenerates electromagnetic energy having a wavelength in a range of 2.70to 2.80 microns; an erbium, yttrium, aluminum garnet (Er:YAG) solidstate laser, which generates electromagnetic energy having a wavelengthof 2.94 microns; chromium, thulium, erbium, yttrium, aluminum garnet(CTE:YAG) solid state laser, which generates electromagnetic energyhaving a wavelength of 2.69 microns; erbium, yttrium orthoaluminate(Er:YAL03) solid state laser, which generates electromagnetic energyhaving a wavelength in a range of 2.71 to 2.86 microns; holmium,yttrium, aluminum garnet (Ho:YAG) solid state laser, which generateselectromagnetic energy having a wavelength of 2.10 microns; quadrupledneodymium, yttrium, aluminum garnet (quadrupled Nd:YAG) solid statelaser, which generates electromagnetic energy having a wavelength of 266nanometers; argon fluoride (ArF) excimer laser, which generateselectromagnetic energy having a wavelength of 193 nanometers; xenonchloride (XeC1) excimer laser, which generates electromagnetic energyhaving a wavelength of 308 nanometers; krypton fluoride (KrF) excimerlaser, which generates electromagnetic energy having a wavelength of 248nanometers; and carbon dioxide (C02), which generates electromagneticenergy having a wavelength in a range of 9 to 11 microns.

Particles, such as electrons, associated with the impurities absorbenergy from the impinging incoherent radiation and rise to highervalence states. The particles that rise to metastable levels remain atthis level for periods of time until, for example, energy particles ofthe radiation excite stimulated transitions. The stimulation of aparticle in the metastable level by an energy particle results in bothof the particles decaying to a ground state and an emission of twincoherent photons (particles of energy). The twin coherent photons canresonate through the laser rod between mirrors at opposing ends of thelaser rod, and can stimulate other particles on the metastable level, tothereby generate subsequent twin coherent photon emissions. This processis referred to as light amplification by stimulated emission. With thisprocess, a twin pair of coherent photons will contact two particles onthe metastable level, to thereby yield four coherent photons.Subsequently, the four coherent photons will collide with otherparticles on the metastable level to thereby yield eight coherentphotons.

The amplification effect will continue until a majority of particles,which were raised to the metastable level by the stimulating incoherentlight from the flashlamp 41, have decayed back to the ground state. Thedecay of a majority of particles from the metastable state to the groundstate results in the generation of a large number of photons,corresponding to an upwardly rising micropulse (64, for example, FIG.5). As the particles on the ground level are again stimulated back up tothe metastable state, the number of photons being emitted decreases,corresponding to a downward slope in the micropulse 64, for example. Themicropulse continues to decline, corresponding to a decrease in theemission of coherent photons by the laser system. The number ofparticles stimulated to the metastable level increases to an amountwhere the stimulated emissions occur at a level sufficient to increasethe number of coherent photons generated. As the generation of coherentphotons increases, and particles on the metastable level decay, thenumber of coherent photons increases, corresponding to an upwardlyrising micropulse.

The output optical energy distribution over time of the laser system isillustrated in FIG. 5 at 60. The output optical energy distribution ofthe present invention preferably has a pulse width that is greater thanabout 0.25 microseconds and, more preferably, in a range of 125 to 300microseconds. In the illustrated embodiment, the pulse width is about200 microseconds. The output optical energy distribution 60 comprises amaximum value 62, a number of leading micropulses 64, 66, 68, and aportion of generally declining optical energy 70.

According to the present invention, the output optical energydistribution 60 comprises a large magnitude. This large magnitudecorresponds to one or more sharply-rising micropulses at the leadingedge of the pulse. As illustrated in FIG. 5, the micropulse 68 comprisesa maximum value 62 which is at or near the very beginning of the pulse.Additionally, the full-width half-max value of the output optical energydistribution in FIG. 5 is approximately 70 microseconds, compared tofull-width half-max values of the prior art typically ranging from 250to 300 microseconds. Applicant's invention contemplates pulsescomprising full-width half-max values greater than 0.025 microsecondsand, preferably, ranging from 10 to 150 microseconds, but other rangesmay also be possible. Additionally, Applicant's invention contemplates apulse width of between 0.25 and 300 microseconds, for example, comparedto typical prior-art pulse widths which are greater than 300microseconds. Further, a frequency of 20 Hz is presently preferredalternatively, a frequency of 30 Hz may be used. Applicants' inventiongenerally contemplates frequencies between 1 and 100 Hz, compared toprior art frequencies typically ranging from 1 to 15 Hz.

As mentioned above, the full-width half-max range is defined from abeginning time, where the amplitude first rises above one-half the peakamplitude, to an ending time, where the amplitude falls below one-halfthe peak amplitude a final time during the pulse width. The full-widthhalf-max value is defined as the difference between the beginning timeand the ending time.

The location of the full-width half-max range along the time axis,relative to the pulse width, is closer to the beginning of the pulsethan the end of the pulse. The location of the full-width half-max rangeis preferably within the first half of the pulse and, more preferably,is within about the first third of the pulse along the time axis. Otherlocations of the full-width half-max range are also possible inaccordance with the present invention. The beginning time preferablyoccurs within the first 10 to 15 microseconds and, more preferably,occurs within the first 12.5 microseconds from the leading edge of thepulse. The beginning time, however, may occur either earlier or laterwithin the pulse. The beginning time is preferably achieved within thefirst tenth of the pulse width.

Another distinguishing feature of the output optical energy distribution70 is that the micropulses 64, 66, 68, for example, compriseapproximately one-third of the maximum amplitude 62. More preferably,the leading micropulses 64, 66, 68 comprise an amplitude ofapproximately one-half of the maximum amplitude 62. In contrast, theleading micropulses of the prior art, as shown in FIG. 2, are relativelysmall in amplitude.

The slope of the output optical energy distribution 60 is greater thanor equal to 5 and, more preferably, is greater than about 10. In theillustrated embodiment, the slope is about 50. In contrast, the slope ofthe output optical energy distribution 20 of the prior art is about 4.

The output optical energy distribution 60 of the present invention isuseful for maximizing a cutting effect of an electromagnetic energysource, such as a laser, directed into an atomized distribution of fluidparticles above a target surface. An apparatus for directingelectromagnetic energy into an atomized distribution of fluid particlesabove a target surface is disclosed in co-pending U.S. application Ser.No. 08/522,503, filed Aug. 31, 1995 and entitled USER PROGRAMMABLECOMBINATION OF ATOMIZED PARTICLES FOR ELECTROMAGNETICALLY INDUCEDCUTTING. The high-intensity leading micropulses 64, 66, and 68 impartlarge amounts of energy into atomized fluid particles which preferablycomprise water, to thereby expand the fluid particles and applymechanical cutting forces to the target surface. The trailingmicropulses after the maximum micropulse 68 have been found to furtherenhance the cutting efficiency. According to the present invention, asingle large leading micropulse 68 may be generated or, alternatively,two or more large leading micropulses 68 (or 64, 66, for example) may begenerated.

The flashlamp current generating circuit 30 of the present inventiongenerates a relatively narrow pulse, which is on the order of 0.25 to300 microseconds, for example. Additionally, the full-width half-maxvalue of the optical output energy distribution 60 of the presentinvention preferably occurs within the first 70 microseconds, forexample, compared to full-width half-max values of the prior artoccurring within the first 250 to 300 microseconds. The relatively quickfrequency, and the relatively large initial distribution of opticalenergy in the leading portion of each pulse of the present invention,results in efficient mechanical cutting. If a number of pulses of theoutput optical energy distribution 60 were plotted, and the averagepower determined, this average power would be relatively low, comparedto the amount of energy delivered to the laser system via thehigh-voltage power supply 33. In other words, the efficiency of thelaser system of the present invention may be less than typical prior artsystems. Since the output optical energy distributions of the presentinvention are uniquely adapted for imparting electromagnetic energy intoatomized fluid particles over a target surface, however, the actualcutting of the present invention is optimized. The cutting effectobtained by the output optical energy distributions of the presentinvention is both clean and powerful and, additionally, provides aconsistent cut. The terms “cut” and “cutting” are broadly defined hereinas imparting disruptive mechanical forces onto the target surface.

In accordance with one aspect of the present invention, an apparatus isprovided, comprising a current generating circuit; an excitation sourceoperatively coupled to the current generating circuit, the excitationsource comprising at least one laser diode and being configured tooperate at a frequency within a range from about 1 to about 100 Hz; anda gain medium coupled to be side pumped by the excitation source and tooutput electromagnetic energy.

Accordance to another aspect of the present invention, a method isprovided, comprising providing a current generating circuit; providingan excitation source operatively coupled to the current generatingcircuit, the excitation source comprising at least one laser diode andbeing configured to operate at a frequency within a range from about 1to about 100 Hz; and activating the excitation source to side pump again medium, whereby the gain medium outputs electromagnetic energy.

In accordance with another aspect of the present invention, an apparatusfor cutting or ablating hard tissue comprises an optical cavity; a gainmedium disposed within the optical cavity; and a diode light pumpdisposed within the optical cavity and optically aligned to light pumpthe gain medium to generate laser light, wherein the generated laserlight has a wavelength and power density suitable for cutting andablating hard tissue.

A method of cutting or ablating hard tissue according to a furtheraspect of the present invention comprises the steps of providing a gainmedium, a diode light pump, and an optical cavity; placing the gainmedium and the diode light pump within the optical cavity so that thediode light pump is optically aligned to light pump the gain medium;activating the diode light pump to light pump the gain medium andgenerate laser light; and directing the laser light onto the hard tissueto cut or ablate the hard tissue.

According to another aspect of the invention, a method of cutting orablating hard tissue is disclosed, comprising the steps of providing again medium, a diode array, and an optical cavity; placing the gainmedium and the diode array within the optical cavity so that the diodearray is optically aligned to side pump the gain medium; activating thediode array to light pump the gain medium and generate laser light; anddirecting the laser light onto the hard tissue to cut or ablate the hardtissue.

An apparatus for imparting disruptive forces onto a target surface,according to another aspect, comprises: a fluid output configured toplace fluid into a volume in close proximity to the target surface; andan excitation source configured to direct electromagnetic energy intothe volume in close proximity to the target surface, wherein theexcitation source outputs the electromagnetic energy in a form of atleast one output pulse having a plurality of high-intensity leadingmicropulses that impart relatively large amounts of energy into at leastpart of the fluid in the volume, the relatively large amounts of energyimparted into the fluid being sufficient to cause the fluid to expandwherein disruptive cutting or ablating forces onto to the targetsurface, the excitation source being configured to operate at afrequency within a range from about 1 to about 100 Hz.

A method of cutting or ablating hard tissue is also provided inaccordance with an aspect of the present invention, comprising thefollowing steps: placing fluid into a volume in close proximity to thehard tissue; and activating an excitation source comprising at least onelaser diode to light pump a gain medium and generate laser light in aform of at least one output pulse having a plurality of high-intensityleading micropulses, the laser light having a wavelength which is highlyabsorbed by the fluid, the excitation source being configured to operateat a frequency within a range from about 1 to about 100 Hz. The methodcan comprise directing the at least one output pulse into the volume toimpart relatively large amounts of energy into at least part of thefluid in the volume, the relatively large amounts of energy causing thefluid to expand wherein disruptive cutting or ablating forces areimparted to the target surface.

In any of the above aspects, the gain medium may comprise a laser rod,such as an Erbium-based laser rod. More particularly, the gain mediummay comprise an Erbium-based crystalline laser rod for generating laserlight in a range between 1.73 and 2.94 microns. The laser light can havea wavelength in a range from about 2.69 um to about 2.95 um.

The laser light can be generated in the TEMoo mode to overcome thermaleffects. The generated laser light can have a wavelength, pulse, andpower density suitable for cutting and ablating tooth tissue or bone.Thus, in accordance with a method of the present invention, the hardtissue can comprise, for example, tooth or bone tissue. Temporal pulsecontrol can be used to attain a uniform temporal pulse pattern. Inanother embodiment, gain switching or Q-switching can be used to attainthe uniform temporal pulse pattern. The diode light pump or the at leastone diode can comprise a diode array, and the diode array can beoptically aligned to side pump the gain medium. The diode light pump canbe placed within the optical cavity so that the diode array is opticallyaligned to side pump the gain medium. The generated laser light can havea wavelength that is highly absorbed by the fluid. The fluid cancomprise water.

The methods and apparatuses of this application are intended for use, tothe extent the technology is compatible, with existing technologiesincluding the apparatuses and methods disclosed in any of the followingpatents and patent applications: U.S. Pat. Nos. 7,108,693; 7,068,912;6,942,658; 6,829,427; 6,821,272; 6,744,790; 6,669,685; 6,616,451;6,616,447; 6,610,053; 6,567,582; 6,561,803; 6,544,256; 6,533,775;6,389,193; 6,350,123; 6,288,499; 6,254,597; 6,231,567; 6,086,367;5,968,037; 5,785,521; and 5,741,247; and U.S. application Ser. Nos.10/858,557, filed Jun. 1, 2004 and 10/178,080, filed Jun. 21, 2002, theentire contents of all which are incorporated herein by reference.

The diode side pumped Erbium crystalline laser of the present inventionmay emit at wavelengths between 1.73 and 2.94 μm. The pumping may beaccomplished by InGaAs laser diodes configured as bars or arraysemitting at 968 nm, and can be delivered in either a CW (continuouswave) or a QCW (quasi-continuous wave) mode of operation, at powerlevels that may begin at 40 W. With an optimized output coupling, thelight-to-light efficiency can be at least 10% and can reach a magnitudeup to 35%. One of the embodiments of this invention is that theseefficiency magnitudes are higher than those which may have beenpreviously attained, owing to the inventive design which seeks tomaximize the pump-to-laser mode overlap and to optimize outcoupling,specifically tailoring the outcoupling to the pulse format or CWoperation of the laser.

The oscillator of the present invention is a plano-plano resonatorcomprising a high reflectivity mirror and an outcoupling, partiallytransmitting mirror. For certain applications intracavity elements, suchas an electro-optic or acousto-optic cell for Q-switching, or an etalonfor wavelength tuning can be introduced. The laser can emit energy in,for example, one of the following modes of operation: CW, gain switchedobtained by quasi-CW operation of the pump laser diode, and Q-switchedby an acousto-optical (AO) device or Q-switched by an electro-optical(EO) device. Thermal management and temperature control are provided byeither air and/or water cooling, with the possibility of usingthermo-electric cooling.

In the category of the disclosed diode side pumped lasers included arethe following crystals: Er:LiYF₄ (Er:YLF) emitting at 1.73 μm on theEr³⁺⁴I_(13/2)

⁴I_(15/2) transition; Er:LiYF₄ emitting at 2.80 μm on the Er³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:Y₃Sc₂GasO₁₂ (Er:YSGG) emitting at 2.79 μm onthe Er³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:Gd₃Sc₂GasO₁₂ (Er:GSGG) emitting at 2.8 μm onthe Er³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:Gd₃GasO₁₂ (Er:GGG) emitting at 2.82 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er,Tm:Y₃Al₅O₁₂ (TE:YAG) emitting at 2.69 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:KYF₄ emitting at 2.81 μm on the Er³⁺⁴I_(11/2)

⁴I_(13/2) transition; Ho,Yb:KYF₄ emitting at 2.84 μm on the Ho³⁺⁵I₆

⁵I₇ transition; Er:Y₃Al₅O₁₂ (Er:YAG) emitting at 2.94 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:Y₃AlO₃ (Er:YALO) emitting at 2.71 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:KGd(WO₄)_(s) (Er:KGW) emitting at 2.8 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:KY(WO₄)_(s) (Er:KYW); Er:Al₃O₃ emitting on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:Lu₃O₃ emitting at emitting at 2.7 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:CaF₂ emitting at 2.75-2.85 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; Cr,Tm,Er:Y₃Al₅O₁₂ (CTE:YAG) emitting at 2.7 μm onthe Er³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:BaLu₂F₈ emitting at 2.8 μm on the Er³⁺⁴I_(11/2)

⁴I_(13/2) transition; Er:BaY₂F₈ (Er:BYF) emitting at 2.7 μm on theEr³⁺⁴I_(11/2)

⁴I_(13/2) transition; and Cr:ZnSe emitting at 2-3 μm.

Due to their efficient interaction with biological tissue and water,these lasers are useful as surgical instruments, in the areas of, forexample, dental surgery, orthopedic surgery, tissue ablation, bonecutting and soft tissue surfacing. Particular applications may includeuse of the laser for expansion of atomized water or fluid particlesabove a target surface for mechanical cutting or ablation, such asdisclosed in U.S. Pat. No. 5,741,247, entitled Atomized Fluid Particlesfor Electromagnetically Induced Cutting, and U.S. Pat. No. 5,785,521,entitled “Fluid Conditioning System,” the contents of which areexpressly incorporated herein by reference.

Another embodiment of the side diode pumped erbium lasers and Ho,Yb:KYF4laser is that when operated in pulses, the pulsed format is highlyrepetitive in time and intensity. This performance can facilitateprecise and predictable cutting, and can improve cutting efficiency. Indental and medical applications, this feature is consistent with lessheat or thermal denaturation of the tissue, which can provide forquicker healing.

The present invention is configured as shown in FIGS. 1 a, 2 a and 2 b.It applies the side-pumped configuration to: 1) pumping of erbium andHo,Yb:KYF4 crystals to extract laser emission in the 1.73 and 2.94 μmrange, 2) dental and medical cutting and resurfacing by mainly the 2.69to 2.95 μm range, 3) optimization of the dental and medical process byefficient delivery of the laser to the target and minimal thermalprocess. Configuration of the crystal itself can be rectangular orround. A rectangular shape may be preferred in one embodiment, althougha cylindrical shape may function well in modified embodiments. Thepumping wavelength should be chosen to be efficiently transferred intothe crystal, wherein for example the radiation wavelength of the diodepumping source matches a peak absorption of the active media or crystal.In one embodiment a lens may be used to couple the pump source to thelaser rod. Cooling sources and/or lenses may be positioned between thepump source and the laser rod. Regarding FIGS. 2 a and 2 b, FIG. 2 a isa schematic top view of a laser head according to the present inventionwherein “TEC” denotes thermo electric cooler, and FIG. 2 b is aschematic side view of a laser head according to the present inventionwherein opposing ends of the laser rod are cut to the Brewster angle toprovide polarization.

Regarding the present invention's application of the side-pumpedconfiguration to optimize dental and medical processes by efficientdelivery of the laser to the target and minimal thermal process,optimization is accomplished by radiating the target with a train ofwell regulated pulses, as shown in FIG. 3 a. What is shown is a sequenceof narrow pulses, each having a sufficiently high power, for instance 20kW, and an energy of 8 mJ. With a duty cycle of 0.02% this determines anaverage power of 4 W. A number of methods may be employed to attain sucha pulse format, among them: gain switching and Q-switching by either anelectro-optical or an acousto-optical Q-switch.

The Q-switch temporal trace is shown in FIGS. 4 a-4 c, wherein FIG. 4 ashows the population inversion in a CW pumping regime, FIG. 4 b showsthe resonator Q due to the Q-switch hold-off, and FIG. 4 c correspondsgenerally to FIG. 3 a and shows the resulting laser pulse. The gainswitch temporal trace is shown in FIGS. 5 a-5 c, wherein FIG. 5 a showsthe quasi-CW (QCW) current supplied to the pumping laser diode, FIG. 5 bshows the population inversion in the QCW pumping regime and FIG. 5 cshows the resulting laser pulse. Because in gain switching the resonatorQ is never spoiled, the pulse evolves simultaneously with the buildup ofthe population inversion. Hence, the dynamics are similar to a freerunning laser, as in the pulse train shown in FIG. 6. However, as shownin FIG. 5A, the gain is dropped to below threshold once the first spikeis generated, thus a gain switch pulse is formed as the first spikeonly, as shown in FIG. 7. Additional description is provided in thefollowing table.

In view of the foregoing, it will be understood by those skilled in theart that the methods of the present invention can facilitate formationof laser devices, and in particular side-pumped diode laser systems. Theabove-described embodiments have been provided by way of example, andthe present invention is not limited to these examples. Multiplevariations and modification to the disclosed embodiments will occur, tothe extent not mutually exclusive, to those skilled in the art uponconsideration of the foregoing description. Such variations andmodifications, however, fall well within the scope of the presentinvention as set forth in the following claims.

1. An apparatus for imparting forces onto a tissue target surface,comprising: a first component consisting essentially of a fluid outputconfigured to place fluid into a first vicinity relative to the fluidoutput; and a second component consisting essentially of an excitationsource configured to direct electromagnetic energy to a second vicinityfor at least partial absorption by the fluid, the first vicinity and thesecond vicinity intersecting in a volume relative to the fluid output,wherein the excitation source outputs the electromagnetic energy in aform of at least one output pulse having a plurality of high-intensityleading micropulses sufficient to impart relatively large amounts ofenergy into at least part of the fluid in the volume, the relativelylarge amounts of energy imparted into the fluid being sufficient tocause the fluid to expand wherein disruptive cutting or ablating forcesare directed to the tissue target surface.
 2. The apparatus as set forthin claim 1, wherein the excitation source is configured to focus orplace a peak concentration of the electromagnetic energy into the volumeso as to be highly absorbed by at least part of the fluid in the volume.3. The apparatus as set forth in claim 1, further comprising an opticalcavity and a gain medium disposed within the optical cavity, wherein theexcitation source is disposed within the optical cavity and opticallyaligned to light pump the gain medium to generate electromagnetic energyincluding laser light, wherein the generated laser light has awavelength, pulse, and power density suitable for cutting or ablatingthe tissue target surface and further has a wavelength that is highlyabsorbed by the fluid.
 4. The apparatus as set forth in claim 1, whereinthe fluid is water and the tissue target surface comprises hard tissue.5. The apparatus as set forth in claim 1, wherein: the first componentis an atomizer configured to generate a combination of atomized fluidparticles, and to place the combination of atomized fluid particles intothe volume; and the second component is a specifically configuredexcitation source that is arranged, when the apparatus is positioned inuse such that the volume is above the tissue target surface, to supplyelectromagnetic energy of a wavelength which is substantially absorbedby the atomized fluid particles and to focus or place a peakconcentration of the electromagnetic energy into the volume so as to besubstantially absorbed by at least a portion of the combination ofatomized fluid particles to cause the portion of atomized fluidparticles to impart disruptive forces to the tissue target surface. 6.The apparatus as set forth in claim 1, wherein the excitation sourcecomprises one or more of: an Erbium-based crystalline laser rod; afrequency within a range from about 1 to about 100 Hz; laser lighthaving a wavelength, pulse and power density suitable for causingcutting or ablating of tooth tissue; temporal pulse control forattainment of a uniform temporal pulse pattern; and laser light in theTEMoo mode.
 7. The apparatus as set forth in claim 1, wherein the fluidis water and the second component emits electromagnetic energy having awavelength in a range from about 2.69 um to about 2.95 um.
 8. Anapparatus for combining components in a volume to effectuate generationof expansive forces within the volume, the apparatus comprising: a firstcomponent constituting a fluid output that is configured to place fluidinto a first vicinity relative to the fluid output; and a secondcomponent constituting an excitation source that is configured to emitelectromagnetic energy toward a second vicinity for at least partialabsorption by the fluid, the first vicinity and the second vicinityintersecting in a volume relative to the fluid output, wherein theexcitation source outputs the electromagnetic energy in a form of atleast one output pulse having a plurality of high-intensity leadingmicropulses sufficient to impart relatively large amounts of energy intoat least part of the fluid in the volume, the relatively large amountsof energy imparted into the fluid being sufficient to cause the fluid toabsorb at least part of the electromagnetic energy and expand whereinthe expansive forces are generated to propagate in a direction away fromthe apparatus.
 9. The apparatus as set forth in claim 8, wherein theoutput pulse comprises one or more micropulses with a sharply-risingintensity at the leading edge of the output pulse.
 10. The apparatus asset forth in claim 8, wherein the output pulse has an amplitude and apeak amplitude, and wherein the amplitude of the output pulse risesabove one-half of the peak amplitude within the first 15 microsecondsfrom a leading edge of the output pulse.
 11. The apparatus as set forthin claim 8, wherein the output pulse has a peak amplitude and a pulsewidth, and wherein an amplitude of the output pulse rises above one-halfof the peak amplitude within the first tenth of the pulse width.
 12. Theapparatus as set forth in claim 8, wherein the output pulse has amaximum amplitude and each of the leading micropulses has a peakamplitude, and wherein one or more of peak amplitudes is about one-thirdor more of the maximum amplitude.
 13. The apparatus as set forth inclaim 8, wherein each of the leading micropulses has a peak amplitudeand the output pulse has a maximum amplitude, and wherein at least oneof peak amplitudes is about half or more of the maximum amplitude. 14.The apparatus as set forth in claim 8, wherein the components areconfigured and aligned relative to one another to cause, during use,impartation of relatively large amounts of energy into at least part ofthe fluid in the volume, the relatively large amounts of energy causingthe fluid to expand.
 15. The apparatus as set forth in claim 14, whereinduring use when the volume is juxtaposed relative to a tissue targetsurface disruptive forces are imparted to the tissue target surface. 16.An apparatus for combining components in a volume to effectuategeneration of expansive forces within the volume, the apparatuscomprising: an atomizer configured to generate a combination of atomizedfluid particles comprising water, and to place the combination ofatomized fluid particles into a first vicinity relative to the atomizer;and a laser output configured to emit electromagnetic energy having awavelength in a range from about 1.73 um to about 2.95 um in a directiontoward a second vicinity for at least partial absorption by the atomizedfluid particles, the first vicinity and the second vicinity intersectingin a volume relative to the fluid output and the laser output focusing,or placing a peak concentration of, the electromagnetic energy into thevolume, wherein the laser output emits the electromagnetic energy in aform of at least one output pulse having a plurality of high-intensityleading micropulses sufficient to impart relatively large amounts ofenergy into at least part of the water in the volume, the relativelylarge amounts of energy imparted into the water being sufficient tocause the atomized fluid particles to absorb at least part of theelectromagnetic energy and expand wherein the expansive forces aregenerated to propagate in a direction at least partially away from theapparatus.
 17. The apparatus as set forth in claim 16, wherein: thefirst component comprises an atomizer configured to generate acombination of atomized fluid particles, and to place the combination ofatomized fluid particles into the volume; and the second componentcomprises a specifically configured excitation source that is arranged,when the apparatus is positioned in use such that the volume is abovethe target surface, to supply electromagnetic energy of a wavelengthwhich is substantially absorbed by the fluid particles and to focus orplace a peak concentration of the electromagnetic energy into the volumeso as to be substantially absorbed by at least a portion of thecombination of atomized fluid particles to cause the portion of atomizedfluid particles to impact disruptive mechanical forces to the targetsurface.
 18. The apparatus as set forth in claim 16, wherein theexcitation source comprises a diode array that is optically aligned toside pump the laser rod.
 19. The apparatus as set forth in claim 16,wherein the excitation source comprises at least one laser diode that isconfigured to operate at a frequency within a range from about 1 toabout 100 Hz.
 20. The apparatus as set forth in claim 16, wherein thetissue target surface comprises one or more of tooth tissue and bone.21. The apparatus as set forth in claim 16, wherein the excitationsource is configured to focus or place a peak concentration of theelectromagnetic energy into the volume so as to be highly absorbed by atleast part of the fluid in the volume.
 22. The apparatus as set forth inclaim 16, wherein: the excitation source comprises an Erbium based laserrod for generating electromagnetic energy having a wavelength in a rangefrom about 1.73 um to about 2.95 um; and the fluid comprises water.